Turbulence-Resistant FSO Communication Using a Few-Mode Pre-Amplified Receiver

Liu, Huiyuan; Huang, Bin; Zacarias, Juan Carlos Alvarado; Wen, He; Chen, Haoshuo; Fontaine, Nicolas K.; Ryf, Roland; Antonio-López, Jose Enrique; Correa, Rodrigo Amezcua; Li, Guifang

doi:10.1038/s41598-019-52698-1

Cited by 14 publications

(10 citation statements)

References 16 publications

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“…One technique is to use adaptive optics wherein the following steps are performed to convert the data power back into the Gaussian mode: (a) the modal-coupling distortion is measured by a wavefront sensor, and (b) a conjugate phase is calculated by digital signal processing (DSP) and subsequently applied in a feedback loop to the data beam by a wavefront corrector 16 . Another technique is to use multi-mode digital coherent combining [17][18][19] , wherein much of the data power in higher-order modes is captured by either a multi-mode fiber 20 or an array of SMF-based apertures 19 . Subsequently, the data power from each of multiple modes is typically recovered by a separate coherent detector with its own PD, LO (perhaps shared amongst many detectors), and DSP [17][18][19] .…”

Section: Introductionmentioning

confidence: 99%

Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Zhang

Zhou

et al. 2021

Nat. Photon.

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In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to higher-order modes, resulting in a significantly degraded mixing efficiency and system performance. Here, we use a pilot-assisted self-coherent detection approach to overcome this problem. Specifically, we transmit both a Gaussian data beam and a frequency-offset Gaussian pilot tone beam such that both beams experience similar turbulence and modal coupling. Subsequently, a photodetector mixes all corresponding pairs of the beams’ modes. During mixing, a conjugate of the turbulence-induced modal coupling is generated and compensates the modal coupling experienced by the data, and thus the corresponding modes of the pilot and data mix efficiently. We demonstrate a 12 Gbit s−1 16-QAM polarization-multiplexed free-space optical link that is resistant to turbulence.

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Section: Introductionmentioning

confidence: 99%

Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Zhang

Zhou

et al. 2021

Nat. Photon.

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“…The optical signal traveling through the open-air medium is collected at a certain point using the collimating lens setup, which is then filtered with a bandpass filter that restricts the outlier wavelengths and forwards the filter output through a gain optimizer setup. The setup helps amplify the signal by an input from a pump LASER emitting the wavelength that is the same as the output toned by a bandpass filter [48]. The coupled output is passed through erbium-doped fiber that helps in the amplification of optical signals without loss of intended information.…”

Section: Link Design Analyticsmentioning

confidence: 99%

“…Later, a set of collimating optics can be used to transmit the modulated optical signal for detection and further analysis. This practice not only helps in delivering an all-optical system that is capable of compensating for the loss of signal quality due to atmospheric adversities but also readily integrates with the existing optical backbone networks [48][49][50].…”

Section: Link Design Analyticsmentioning

confidence: 99%

Developing Cost-Effective and High-Speed 40 Gbps FSO Systems Incorporating Wavelength and Spatial Diversity Techniques

et al. 2021

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Free-space optical (FSO) communication systems are being anticipated to offer promising alternatives to existing radio networks in delivering high-speed data access to end-users. Ease of installation, robust features, and cost-effective operation have been the hallmark of FSO systems, and these features will play an obvious role in deciding the ways in which futuristic smart communication models will operate. Despite these arrays of features, FSO links suffer severe performance degradation due to channel-induced impairments caused by atmospheric effects such as rain, haze, and fog. In this work, we have investigated and compared the performance of 40 Gbps FSO links for different channel conditions ranging from clear weather to severe attenuation by incorporating spatial and wavelength diversity as performance booster techniques. The use of an erbium-doped fiber amplifier (EDFA) with FSO links has also been proposed here. Using performance metrics like bit error rate (BER) and eye patterns, it has been found that the use of EDFA not only helps in compensating for the link losses but also aids in realizing an all-optical processing based last-mile access system. The proposed FSO system will be capable of bridging the existing backbone fiber networks with end-users with minimal changes to the existing hardware regime, thereby proving to be extremely cost-effective in sharp contrast to radio-frequency generations which require major infrastructure overhaul.

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“…Since that both downlink and uplink PAM4 data signals are transmitted by the same SMF, the Rayleigh backscattering (RB) noise is considered in this two-way PAM4-based fibre-FSO converged system 19 – 21 . Additionally, the link availability of FSO communications greatly relies on weather conditions which influence the signal intensity 22 , 23 . Thus, atmospheric turbulence because of heavy rain is concerned in a 500-m free-space transmission.…”

Section: Introductionmentioning

confidence: 99%

A two-way 224-Gbit/s PAM4-based fibre-FSO converged system

Tsai

et al. 2022

Sci Rep

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A two-way 224-Gbit/s four-level pulse amplitude modulation (PAM4)-based fibre-free-space optical (FSO) converged system through a 25-km single-mode fibre (SMF) transport with 500-m free-space transmission is successfully constructed, which adopts injection-locked vertical-cavity surface-emitting lasers with polarisation-multiplexing mechanism for a demonstration. Compared with one-way transmission, two-way transmission is an attractive architecture for fibre-FSO converged system. Two-way transmission over SMF transport with free-space transmission not only reduces the required number of fibres and the setups of free-space transmission, but also provides the advantage of capacity doubling. Incorporating dual-wavelength four-level pulse amplitude modulation (PAM4) modulation with polarisation-multiplexing mechanism, the transmission capacity of fibre-FSO converged system is significantly enhanced to 224 Gbit/s (56 Gbit/s PAM4/wavelength × 2-wavelength × 2-polarisation) for downlink/uplink transmission. Bit error rate and PAM4 eye diagrams (downstream/upstream) perform well over 25-km SMF transport with 500-m free-space transmission. This proposed two-way fibre-FSO converged system is a prominent one not only because of its development in the integration of fibre backbone with optical wireless extension, but also because of its advantage in two-way transmission for affording high downlink/uplink data rate with good transmission performance.

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Turbulence-Resistant FSO Communication Using a Few-Mode Pre-Amplified Receiver

Cited by 14 publications

References 16 publications

Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Turbulence-resilient pilot-assisted self-coherent free-space optical communications using automatic optoelectronic mixing of many modes

Developing Cost-Effective and High-Speed 40 Gbps FSO Systems Incorporating Wavelength and Spatial Diversity Techniques

A two-way 224-Gbit/s PAM4-based fibre-FSO converged system

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